View source for WinInvalidateRegion

This function ''adds a region to a window's update region''.

==Syntax==
 WinInvalidateRegion(hwnd, hrgn, fIncludeChildren)

==Parameters==
;hwnd ([[HWND]]) - Input: Handle of the window whose update region is to be changed. Use HWND_DESKTOP for the entire screen.
;hrgn ([[HRGN]]) - Input: Handle of the region to be added to the update region. Use NULLHANDLE to invalidate the entire window.
;fIncludeChildren ([[BOOL]]) - Input: Invalidation scope indicator.
:;TRUE
::Include the descendants of ''hwnd'' in the invalid region.
:;FALSE
::Include descendants only if the parent window does not have the WS_CLIPCHILDREN style.
;rc ([[BOOL]]) - Returns: TRUE for successful completion, FALSE for error.

==Returns==
;rc (BOOL) - returns :Success indicator.
:;TRUE
::Successful completion
:;FALSE
::Error occurred.

==Remarks==
The update region is a portion of a window that needs to be redrawn because it is considered "invalid" or visually incorrect.

If the window has the CS_SYNCPAINT style, it is redrawn during this function call, and the update region should be NULL upon return.

If a window with the WS_CLIPCHILDREN style has an update region overlapping child windows with CS_SYNCPAINT, those children are updated before this function returns.

Do not call this function in response to a [[WM_PAINT]] message for windows with the CS_SYNCPAINT style. This would lead to an infinite loop of invalidation and paint messages.

==Errors==
Possible returns from [[WinGetLastError]]:
:* PMERR_INVALID_HWND (0x1001) - An invalid window handle was specified.
:* PMERR_HRGN_BUSY (0x2034) - An internal region busy error occurred due to concurrent access from different threads.
:* PMERR_INVALID_FLAG (0x1019) - An invalid flag was set for a parameter. Use defined constants.

==Example Code==
<Pre>
#define INCL_WINWINDOWMGR   /* Window Manager Functions     */
#include <os2.h>

HWND    hwnd;       /* window handle                    */

WinInvalidateRegion(hwnd, NULLHANDLE, 0);
</Pre>
This example invalidates the entire window. To invalidate a subregion, replace NULLHANDLE with a valid region handle.

==Related Messages==
* [[WM_PAINT]]

==Related Functions==
* [[WinBeginPaint]]
* [[WinEnableWindowUpdate]]
* [[WinEndPaint]]
* [[WinExcludeUpdateRegion]]
* [[WinGetClipPS]]
* [[WinGetPS]]
* [[WinGetScreenPS]]
* [[WinInvalidateRect]]
* [[WinIsWindowShowing]]
* [[WinIsWindowVisible]]
* [[WinLockVisRegions]]
* [[WinOpenWindowDC]]
* [[WinQueryUpdateRect]]
* [[WinQueryUpdateRegion]]
* [[WinRealizePalette]]
* [[WinReleasePS]]
* [[WinShowWindow]]
* [[WinUpdateWindow]]
* [[WinValidateRect]]
* [[WinValidateRegion]]
[[Category:Win]]